RASSF1A lacks apparent enzymatic activity but contains a Ras association (RA) domain and is potentially an effector of the Ras oncoprotein. RASSF1A modulates multiple apoptotic and cell cycle checkpoint pathways. Current evidence supports the hypothesis that it serves as a scaffold for the assembly of multiple tumor suppressor complexes and may relay pro-apoptotic signaling by KRas. RASSF1A is part of a family of potential tumor suppressorsRASSF1A is a member of a family of six related proteins, each of which exhibits multiple splice variants. With the exception of some minor splice variants, each protein contains an RA domain and a C-terminal SARAH protein-protein interaction motif. Each family member, with the exception of RASSF3, has now been implicated as a human tumor suppressor. RASSF5 (Nore1a) is the best characterized member of the family after RASSF1A. RASSF5 was the first member of the family cloned and it was originally designated Nore1a for novel Ras effector 1 (Vavvas et al., 1998). RASSF5 binds activated Ras directly and is present in an endogenous complex with Ras in cells. RASSF5 is pro-apoptotic and kills cells in a Ras-dependent manner (Khokhlatchev et al., 2002;Vos et al., 2003a). It is frequently inactivated in human tumors by promoter methylation (Table 2). Moreover, it is linked to the development of a rare familial form of cancer (Chen et al., 2003), which confirms its role as a tumor suppressor in vivo. Its mechanisms of action remain largely unknown, although it may regulate the pro-apoptotic kinase MST1 (Praskova et al., 2004). A smaller splice version of RASSF5 has been identified and designated Nore1b or RAPL (Katagiri et al., 2003;Tommasi et al., 2002). This protein demonstrates more restricted expression than RASSF5 and can form an endogenous complex with the Ras-related protein Rap. It regulates lymphocyte adhesion and has also been implicated as a tumor suppressor (Katagiri et al., 2003;Macheiner et al., 2006).RASSF2 is a pro-apoptotic Ras effector that is frequently downregulated in human tumors by promoter methylation, histone deacetylation and sometimes deletion (Akino et al., 2005; Endoh et al., 2005; Hesson et al., 2005; Lambros et al., 2005;Vos et al., 2003b). Inactivation of RASSF2 correlates with activation of Ras in tumor cells (Hesson et al., 2005). Reintroduction of RASSF2 into tumor cells impairs tumorigenesis and knocking down RASSF2 enhances tumorigenesis (Akino et al., 2005). Thus, RASSF2 also appears to be an epigenetically inactivated tumor suppressor. The effector pathways controlled by it remain unknown.RASSF3 can also bind to Ras and inhibit cell growth (unpublished observations). However, it is the only family member whose RNA is not downregulated in tumors (Tommasi et al., 2002). Whether it is involved in tumor suppression thus remains unknown. RASSF4 is frequently downregulated by promoter methylation in human tumor cells, binds to Ras and induces apoptosis. It localizes mostly to the cytosol but can be recruited to the plasma membrane by activated Ras ...

SUMMARY Advanced stage papillary serous tumors of the ovary are responsible for the majority of ovarian cancer deaths, yet the molecular determinants modulating patient survival are poorly characterized. Here, we identify and validate a prognostic gene expression signature correlating with survival in a series of microdissected serous ovarian tumors. Independent evaluation confirmed the association of a prognostic gene microfibril-associated glycoprotein 2 (MAGP2) with poor prognosis, whereas in vitro mechanistic analyses demonstrated its ability to prolong tumor cell survival and stimulate endothelial cell motility and survival via the αVβ3 integrin receptor. Increased MAGP2 expression correlated with microvessel density suggesting a proangiogenic role in vivo. Thus, MAGP2 may serve as a survival-associated target.